Sounds like you're completely on track, just keep your patience and trust that he's getting the hang of using the potty.
I urge you to resist the juice temptation. It isn't really 'necessary' although it could help increase urination frequency. the only reason you'd do it (if you haven't given juice this far) is to correct some perceived problem, but your child doesn't have a 'problem', he just doesn't pee often.
As long as he seems happy and healthy not having to go pee all the time (like he's not holding anything in because of a UTI or something) then there is no need to worry about his frequency. One of my daughters goes 2-3 times a day, the other 3-5, and their niece goes 7-12. all three are healthy happy kids, and all three did potty train quickly!
Our # 2 peed 3 times the whole first day of potty training wake-up to bed-time - not at all the amount of times we thought she should go in order to get the 'habit' of using a toilet (and juice even (eeks) soda her dad gave her didn't increase that). Conversely, it wasn't so much of a hassle to go out during day 2 and 3 of 'training' because she just didn't 'go' so there were no accidents (in the car at least).
(And for those dealing with potty training for the first time, accidents outside of the house do not have to be traumatic or feared if you are prepared to treat it as an 'accident' but not the end of the world - extra diapers/cloths to soak up any accidents in the car seat (or where accident happened) and can be sat upon on the return trip home, a couple changes of underwear, shirts and pants in the trunk and a place to put the soiled clothes. A thing that was more helpful for me dealing with training #1 - since she frequently did need to go potty while out and about - was to take the training potty in the trunk and let her use that one there, rather than have to frantically look around for a toilet for her to use (we used liners in the potty so we didn't have to wash out the waste every time - not the most environmentally ideal, but it is an option).
Keep up the good work!